The invention relates to an actuating device for regulating a control mechanism which is subjected to a force against the direction of regulation. Said actuating device comprises a drive device which has a drive shaft and is connected in a moveable manner to a rotating spindle, by which means an actuating element can be axially displaced in the direction of regulation, in a housing receiving the device.
Such an actuating device is, for example, known from EP 1 024 422. Such actuating devices are used especially for regulating control devices such as valves, throttle devices and other control mechanisms, especially in applications in oil and gas production. The actuating device is used for maritime and terrestrial locations which may be remote or have difficult access. By displacing the actuating element using the rotating spindle, a valve, for example, is closed or appropriately opened as a control device. Generally in this connection, such a valve is subjected to a force in the direction of the open position, produced by a spring element or similar. To regulate the rotating spindle, it is connected in a movable manner to a drive shaft which is driven by a drive device for regulating the rotating spindle and correspondingly the actuating element in the regulation direction. The actuating device comprises a device housing in which essentially all parts of the actuating device are accommodated and protected against harsh ambient effects in appropriate regions of deployment of the actuating device.
Generally, the point of use of such actuating devices is positioned remotely to the associated monitoring and motor control device and additionally it is usually difficult to access, such as for example, with maritime oil and gas production in which the actuating device and the associated control device are located on the sea bed. In order to be able to operate the control device even during a failure or with insufficient effect from the actuating device, a second independent actuating device can be assigned to the same control device. This means that with the failure of one actuating device the other one is employed and remotely operated appropriate to the actuation of the control device.
The constructive complexity and financial cost for the arrangement of two actuating devices for only one control device is quite high. In addition, in this case both actuating devices must be maintained and installed at the location of use, whereby often insufficient space is available.
The object of the application is therefore to improve an actuating device of the type mentioned at the beginning such that actuation of the control device is ensured in a constructively simple and less expensive manner.
U.S. Pat. No. 4,179,944 shows an actuating device with a drive shaft for driving a throttle. The drive shaft is arranged displaceable within a guide sleeve, whereby suitable balls are provided between these two as a bearing. The drive shaft can be withdrawn by rotating a motor and fed forward by rotating a second motor. Appropriate armature windings are provided for both motors and an additional device for fixing a spindle nut is provided between the motors.
In the normal operating mode the armature windings of the motors are separate from one another, whereby a suitable locking pin engages the spindle nut. With the occurrence of a fault, one motor rotates in the clockwise direction and the other motor in the counter-clockwise direction so that the corresponding armature windings move towards one another to move the locking pin into a release position. Then, the spindle nut can move in the longitudinal direction of the drive shaft.
Accordingly, both motors are not used to mutually substitute one another, to move the drive shaft in both directions of rotation or, should the occasion arise, to drive the drive shaft together in both directions of rotation.
The object of the application is therefore to improve an actuating device of the type mentioned at the beginning such that actuation of the control device is ensured in a constructively simple and less expensive manner.